Material supply system in semiconductor device manufacturing plant

ABSTRACT

In a small scaled plant intended for flexible manufacturing, a pure water supply system is provided at a low cost without reducing a production efficiency. A pure water system produces a plurality of grades of pure water which are supplied through pipes connected to points of use for cleaning, CMP, lithography, and the like. Upon receipt of a request signal from each point of use for starting to use a certain grade of pure water, a controller determines whether or not a required amount exceeds the capacity of the grade of pure water which can be supplied by the pure water system. If not, the controller sends a use permission signal to the point of use for permitting the same to use the pure water. When a certain use point is using the requested grade of pure water, the controller may not permit the requesting point of use to use the pure water until a use end signal is sent from the use point which is using the pure water.

TECHNICAL FIELD OF THE INVENTION

The present invention relates to semiconductor device manufacturingtechnologies, and more particularly to a material supply system forsupplying processing facilities in a semiconductor device manufacturingplant with materials which include gases, liquids and solids. It shouldbe first noted that the term “materials” used in this specificationinclude gases and liquids for use in processing facilities forprocessing semiconductor wafers and cleaning the processing facilitiesthemselves such as material gases and chemical, as well as gases,liquids and granular solids which are not directly used for reactionssuch as cooling water for pumps associated with the processingfacilities, heaters for heating reaction chambers, and the like.

BACKGROUND ART

Conventional semiconductor device manufacturing plants are generallylarge in scale for relying on the mass production to reduce productioncosts. For example, one known manufacturing plant is capable ofproducing 1,000 lots (one lot includes 100 wafers) per month. In such alarge scale plant, there are installed more than several hundred mainapparatuses (equipments), and it would typically include more than onehundred points of use which are processing facilities that use purewater for processing.

FIG. 1 illustrates a pure water supply system which is an example ofconventional material supply system. A pretreatment equipment 1introduces a coagulants and the like into raw water, filters the rawwater to remove turbid components included in the raw water, and storesthe filtered water in a filtered water tank 2. Next, a primary purewater system 3 mainly removes ion components included in the filteredwater from the pretreatment equipment 1 (and recovered water from arecovery system 7) to produce primary pure water which is stored in purewater tank 4. Next, an ultrapure water system (i.e., a subsystem) 5further refines the primary pure water from the primary pure watersystem 3 to produce ultrapure water. The ultrapure water is supplied toa variety of points of use 6 in a semiconductor device manufacturingplant. Dilute waste water such as rinse water from the points of use 6is recovered by the recovery system 7, and partially stored in thefiltered water tank 2, depending on the condition of the recoveredwater, for reuse in the primary pure water production in the primarypure water system 3, and partially stored in a reuse tank 8 for reuse inthe facilities of the plant as appropriate. Waste water other than thedilute waste water exhausted from the points of use 6 is processed in awaste water processing system 9 before it is emitted. In this event,solid components in the waste water are dehydrated and wasted as sludge.

The ultrapure water produced in the foregoing manner is supplied to allthe points of use 6.

In the following description, the “primary pure water” and “ultrapurewater” are represented by “pure water” when they are collectivelyreferred to.

In recent years, however, semiconductor products have been increasinglyrequired in a wider number of applications, including products forpersonal computers to digital electric appliances such as portabletelephones, but they tend to have shorter life cycles. To meet thistrend, a shift has been made from mass production to flexible productionin the production of semiconductor products, and moreover, theproduction is required to be agile. A production method proposed to meetthe requirements is a small-scaled semiconductor device manufacturingplant (hereinafter called the “small-scaled plant”). The small-scaledplant, however, is required to be as cost-competitive as a large-scaledsemiconductor device manufacturing plant (hereinafter called the“large-scaled plant”), in addition to the requirement that it be capableof flexible production.

In regard to a pure water supply system in the small-scaled plant, asimple reduction in scale of the pure water supply system generallyinstalled in a large-scaled plant would cause an increase in theproduction cost of pure water per unit (initial cost and running cost)which is reflected to a production cost of semiconductor products.

Such problems implied in the small-scaled plant are not limited to thesupply of pure water, but may apply to the supply of materials such asmaterial gases and chemicals for use in processing of semiconductorwafers, gases and liquids for washing processing facilities, coolingwater for pumps associated with the processing facilities and heatersfor heating reaction chambers, and the like.

On the other hand, in conventional semiconductor device manufacturingprocesses, a variety of processing facilities in the plant use numerousmaterial gases, chemicals and solvents as required by particularprocesses. These materials are generally supplied from cylindercabinets, gas generators, storage tanks for storing chemicals andsolvents, and refiners such as ion exchangers through gas pipes orchemicals pipes routed over the plant, respectively. The supplyfacilities such as the cylinder cabinets, gas generators, storage tanksfor storing chemicals and solvents, refiners such as ion exchangers, andthe like must be sufficient in scale to appropriately support the plantin terms of consumption rates of the gases, chemicals and the like usedtherein. This requirement must be applied not only to the supplycapabilities of the supply facilities but also to inner diameters ofpipes, through which the materials are transported to respectivemanufacturing apparatuses associated therewith, in conformity to theconsumption rates.

However, in the processing facilities, these material gases, chemicalsand the like are not always consumed at the same rate. For example, inan LPCVD furnace in which a polycrystalline silicon film is deposited ona plurality of substrates in batches by LPCVD, the LPCVD furnace issupplied with a monosilane gas, which is the material of the siliconfilm, only when the silicon film is being deposited. Thus, although nomonosilane gas is consumed when the furnace is evacuated, whensemiconductor wafers are carried on shelf-like boards for processing,and the like, the supply capability of an associated supply facility,and the transport capability of associated piping are designed based onthe flow rate of the monosilane gas when it is being consumed. When tensuch LPCVD equipments are installed in a plant, the supply facilitiesand transport facilities are provided for the ten equipments. Notlimited to those materials which are consumed directly in relation tothe processing of semiconductor wafers, such as the monosilane gas,cooling water for a heater is required only when the heater is operatedfor heating, and less water is required when the heater is not operated.

Furthermore, the diameter of semiconductor wafers used in thesemiconductor manufacturing processes tends to become larger year byyear from a view point of production efficiency, and accordingly largerprocessing chambers are provided in the semiconductor manufacturingplant, causing an increase in the amounts of material gases andchemicals consumed therein. Eventually, large capacities are required tosuch supply facilities and transport facilities in order to supplyrequired amounts of material gases, chemicals and the like, resulting inan increased investment on the facilities.

Thus, a serious problem exists not only in small-scaled plant but inlarge-scaled plant, namely, how to economically run a system forsupplying material gases, chemicals and the like through a reduction incapacity.

DISCLOSURE OF THE INVENTION

The present invention has been made in view of the above-mentionedproblems found in the prior art, and it is an object of the invention toprovide a material supply system in a semiconductor device manufacturingplant which not only entails a low initial cost and running cost, but isalso capable of efficiently supplying processing facilities with justthe required amounts of materials only when they are required forprocessing semiconductor wafers.

To achieve the above object, in a first aspect, the present inventionprovides a material supply system for supplying the same kind of a gas,liquid or solid material to a plurality of processing facilities in asemiconductor device manufacturing plant, the system comprising:

-   -   a material supply source; and    -   a controller for controlling the supply of the material from a        supply source to the processing facilities, such that a total        amount of the material currently used by the plurality of        processing facilities does not exceed an amount of the material        which can be supplied from the supply source, by controlling a        start timing from which the material is supplied to a processing        facility.

In the material supply system in the first aspect according to thepresent invention, it is preferable that at least two of the pluralityof processing facilities are adapted to send to the controller userequest signals for requesting to start using the material, or the userequest signal and use end signals for notifying the end or an endnotice of use of the material, and the controller is adapted todetermine, upon receipt of the use request signal associated with thematerial currently used in at least one processing facility from anotherprocessing facility, whether or not a total amount of the materialrequired by these processing facilities exceeds the amount of thematerial which can be supplied by the supply source, and send a usepermission signal to the other processing facility to permit the otherprocessing facility to use the material when determining that the totalamount does not exceed.

In a second aspect, the present invention also provides a materialsupply system for supplying the same kind of a gas, liquid or solidmaterial to a plurality of processing facilities in a semiconductordevice manufacturing plant, the system comprising:

-   -   a material supply source; and    -   a controller for controlling the supply of the material from a        supply source to a plurality of processing facilities, such that        the material is not used simultaneously by a plurality of        processing facilities by controlling a start timing from which        the material is supplied to a processing facility.

In the material supply system in the second aspect according to thepresent invention, it is preferable that at least two of the pluralityof processing facilities are adapted to send to the controller userequest signals for requesting to start using the material, and use endsignals for notifying the end or an end notice of use of the material,and the controller is adapted to respond to the use request signalassociated with the material currently used in at least one processingfacility from another processing facility by delaying sending a usepermission signal for permitting the other processing facility which hassent the use request signal to use the material, until the controllerreceives the use end signal from the processing facility which is usingthe material.

It is preferable that the material supply source is a pure waterproducing for producing a plurality of quality grades of pure water, andthe controller is adapted to control the supply of pure water to theprocessing facilities on a grade-by-grade basis in the supply system ineach of the first and second aspect according to the invention.

The present invention, in a third aspect, further provides a materialsupply system for supplying a gas, liquid or solid material toprocessing facilities in a semiconductor device manufacturing plant, thesystem comprising:

-   -   a material supply source;    -   a buffer for temporarily storing the material; and    -   a controller for controlling the supply of the material from the        buffer to the processing facilities.

In the material supply system in the third aspect, it is preferable tofurther comprise control means for controlling the state of the materialin the buffer, and/or measuring means for measuring the state of thematerial in the buffer. In addition, it is preferable to furthercomprise means for quantifying the amount of the material required atleast in single batch processing by one of the processing facilities.Further, it is preferable that the buffer is adapted to simultaneouslystore at least two kinds or more of materials, and the system is adaptedto supply the materials in the same buffer to the same processingfacilities.

In the material supply system in the third aspect according to theinvention, it is preferable that materials react in the buffer toproduce a new material, and the new material are supplied to theprocessing facilities from the buffer. Further, it is preferable tofurther comprise control means for controlling the temperature, thepressure, and/or the concentration of a material component in thebuffer. It is preferable that an etching gas is stored in the buffer,and the supply system further comprises means for supplying the etchinggas to cleaning chambers in the processing facilities. It is preferablethat pure water is stored in the buffer, and the supply system furthercomprises means for supplying the pure water to chambers in theprocessing facilities. It is preferable that the material supply systemfurther comprises means for recovering the material discharged from achamber at least one of the processing facilities to store the recoveredmaterial in the buffer.

In the material supply system in each of the first, second and thirdaspects according to the invention, it is preferable that the supplysystem is adapted to supply the material from a single supply source toa plurality of processing facilities. In this case, it is preferablethat the supply source includes a buffer for temporarily storing thematerial.

The invention also provides a semiconductor device manufacturing planthaving a plurality of processing facilities, comprising:

-   -   a material supply system in any one of the first through third        aspects;    -   database for logging and managing processes in each of the        processing facilities; and    -   a CIM-based control system for totally controlling the        semiconductor device manufacturing plant, wherein the control        system sets a supply rate at which the material supply system        supplies the material to the processing facilities, and        priorities for supplying the material among the processing        facilities based on an operation schedule for the processing        facilities, and a semiconductor device manufacturing schedule on        the database.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram illustrating a configuration of a conventionalpure water system;

FIG. 2 is a block diagram illustrating a configuration of a pure watersupply system which is one embodiment of a material supply systemaccording to the present invention;

FIG. 3 is a block diagram illustrating a configuration of a pure watersystem provided in the pure water supply system illustrated in FIG. 2;

FIG. 4 is a table showing exemplary grades of pure water requiredrespectively by cleaning equipments, a CMP equipment and a lithographyequipment which constitute points of use;

FIGS. 5A and 5B are explanatory diagrams-showing an exemplaryrelationship between the amounts of ultrapure water required by twolarge cleaning equipments and the possibility of using the ultrapurewater;

FIGS. 6A and 6B are explanatory diagrams showing an exemplaryrelationship between the amounts of primary pure water required by twolarge cleaning equipments, two small cleaning equipment, and onelithography equipment for the respective apparatuses and five CMPequipment and the possibility of using the primary pure water;

FIG. 7 is a flowchart illustrating an exemplary operation forcontrolling supply of pure water, executed in a controller which isprovided in the pure water supply system illustrated in FIG. 2;

FIG. 8 is a diagram conceptually illustrating a material supply systemfor supplying a material to a polycrystalline or non-crystalline siliconfilm LPCVD equipment according to another embodiment of the presentinvention;

FIGS. 9A to 9C are explanatory diagrams each illustrating an exemplarymethod of measuring a monosilane gas when it is introduced from acylinder cabinet to a gas buffer in the LPCVD equipment illustrated inFIG. 8;

FIGS. 10A to 10C are explanatory diagrams each illustrating an exemplarymethod of introducing a monosilane gas from a monosilane gas buffer to areaction tube in the LPCVD equipment illustrated in FIG. 8;

FIG. 10D is a graph showing a change over time in the concentration ofthe monosilane gas;

FIG. 10E is a graph showing relationships between a deposition rate anda deposition time, and a target film thickness and a deposition time;

FIGS. 11A and 11B are explanatory diagrams each illustrating a method ofintroducing a material from a liquid source and a solid source to thebuffer, respectively, in the LPCVD equipment illustrated in FIG. 8;

FIGS. 12A and 12B are explanatory diagrams each illustrating anexemplary method of introducing a fluorine gas from the buffer to thereaction tube in the LPCVD equipment illustrated in FIG. 8;

FIG. 13 is a block diagram illustrating another embodiment of a materialsupply system according to the present invention which employs aplurality of the LPCVD equipment illustrated in FIG. 8; and

FIG. 14 is a block diagram illustrating a material supply system whichreuses a hydrogen fluoride solution in a chemical cleaning process forsemiconductor wafers according to another embodiment of the presentinvention.

BEST MODE FOR CARRYING OUT THE INVENTION First Embodiment

In the following, a pure water supply system for supplying pure water toa plurality of processing facilities will be described as a firstembodiment of a material supply system in a semiconductor devicemanufacturing plant according to the present invention.

The inventors investigated into pure water supply systems andparticularly noted the following aspects.

-   -   At point of use which use pure water, every point of use        requires a different quality of pure water. In other words, not        all the points of use do require an ultrapure water level for        the water quality.    -   Some of points of use which use pure water require different        qualities of pure water on a process-by-process basis, and do        not require the ultrapure water level for the water quality in        all processes.    -   Since a small-scaled plant has a relatively small number of        points of use, complicated piping is not involved in providing a        plurality of quality grades for pure water and routing a pure        water supply pipe for each grade.    -   Classification of pure water by grade can reduce the amount of        produced pure water such as ultrapure water which entails a high        production cost.    -   Since a small-scaled plant has a relatively small number of        points of use, it is possible to readily know how pure water is        used at each point of use.    -   Since a small-scaled plant has a relatively small number of        points of use, the supply of pure water can be readily        controlled among the points of use.    -   At each point of use, pure water is used for a short time        ranging from several tens of seconds to several minutes, which        translates to several percent to several tens of percent of an        overall process (in operation), in an intermittent or periodic        pattern. In addition, since pure water is used at a relatively        small number of points of use, there is an extremely low        probability that a plurality of points of use simultaneously        require the same grade of pure water. Moreover, a pure water use        pattern (including the grade, amount, and used time) can be        readily found for the overall plant.    -   Even if pure water is required simultaneously at several-points        of use, the pure water is used for an extremely short time at        each point of use on each occasion. Therefore, the production        efficiency is hardly affected in the overall plant even if a        point of use is kept waiting for the supply of pure water until        another point of use finishes using pure water.    -   Since the amount of instantaneously required pure water can be        reduced by detecting the amount of pure water used at each-point        of use, the pure water system can be reduced in scale through        such control.

As described above, in a small-scaled plant, there is an extremely lowprobability of a plurality of point of use simultaneously using the samegrade of pure water. Even if the pure water is required simultaneouslyat several points of use, the pure water is used for an extremely shorttime at each use point on each occasion, so that the productionefficiency is hardly affected in the overall plant even if the points ofuse are supplied with the pure water in order that in such a manner onepoint of use is kept waiting for supply of pure water until anotherpoint of use finishes using the pure water. Also, a pure waterproduction cost can be reduced without exacerbating the productionefficiency by detecting the amount of each grade of pure water requiredby each point of use to provide a maximum of the detected amounts ofpure water (amount of instantaneously required pure water). Furthermore,the amount of instantaneously required pure water can be reduced bydetecting and controlling the amounts of used pure water among thepoints of use, thereby reducing the pure water supply system in scale.

As described above, the pure water supply system, which is oneembodiment of a material supply system according to the presentinvention, is created based on the results of analyses on pure waterwhich is simultaneously used at several points of use in a semiconductordevice manufacturing plant and analyses on quality grades of pure waterrequired at the points of use for respective processes.

FIG. 2 is a block diagram schematically illustrating a configuration ofa pure water supply system according to the present invention which isparticularly useful in a small-scaled plant. The illustrated pure watersupply system comprises a pure water system 10 for producing a pluralityof quality grades of pure water; a controller 20 for controlling supplyof pure water; and equipments 31-33, i.e, points of use which requirepure water in a semiconductor device manufacturing plant. The exemplarypure water supply system includes four cleaning equipments (i.e., twolarge cleaning equipments WET1, WET2 and two small cleaning equipmentsWET3, WET4)31; five chemical mechanical polishing equipments (CMP1-CMP5)32; and one lithography equipment (LITHO) 33 as points of use. Theseequipments are simply called the “points of use 30” when they arecollectively treated. The controller 20 comprises a pure water usedatabase (DB) 21 which stores control information such as informationcommunicated between the controller 20 and pure water system 10,information communicated between the controller 20 and each points ofuse 30, and the like for storage of a pure water supply/use log. Theinformation may be communicated through an arbitrary communication meanssuch as LAN within the plant.

It should be noted that supply piping for supplying pure water, andpiping and recovery processing apparatuses for recovering dilute wastewater discharged from the points of use 30 for recirculation to the purewater system are omitted in FIG. 2 so as to simplify the description.

It should also be understood that a plurality of points of use 30 in thesmall-scaled plant are not limited to the aforementioned types andnumbers of equipments.

As illustrated in FIG. 3, the pure water system 10 comprises a raw watertank 11, a primary pure water system 12, a pure water tank 13, asubsystem (ultrapure water producer) 14, and a circulation system 15. Inthe exemplary configuration illustrated in FIG. 3, the pure water system10 uses city water for the raw water. Alternatively, as in the prior artexample illustrated in FIG. 1, industrial water may be used for rawwater which is filtered by a pretreatment system or the like to providefiltered water. Since a small-scaled plant uses a small amount of rawwater, city water is preferably used for the raw water because it doesnot require an intricate pretreatment step. The primary pure watersystem 12, pure water tank 13 and subsystem 14 are similar to thoseprovided in the prior art pure water system illustrated in FIG. 1.

The circulation system 15 controls the pure water tank 13 and points ofuse 30 to circulate at all times an amount of primary pure water whichensure an instantaneously required amount (which permits a plurality ofpoints of use 30 to simultaneously use the pure water) across a pipingsystem. Specifically, through the control of the circulation system 15,the primary pure water flows through the piping system at all times inthe instantaneously required amount plus a margin, such that each pointof use 30 takes in a required amount of primary pure water from thepiping system for use at a time it requires pure water, and primary purewater not used is returned to the pure water tank 13. The circulationsystem 15 preferably comprises a heat exchanger for cooling the primarypure water which is heated during circulation, a UV lamp device forsterilization and an ultrafiltration membrane(UF). The UV lamp devicefor sterilization entails a sufficiently low initial cost and runningcost, as compared with a UV lamp device for TOC decomposition typicallyprovided in the subsystem 14, so that the installation of thecirculation system 15 results in an extremely small rise in pure waterproduction cost. Also, since the pure water tank 13 is installed at alocation downstream of the primary pure water system 12 for storing theprimary pure water, the primary pure water system 12 can produce anamount of primary pure water which is set to an average amount (minimumamount) required by the overall plant.

The foregoing components, which make up the pure water system 10, arepreferably implemented by separate functional modules which can beoperated independently of one another. Such separate functional modulesallow for adaptable ultrapure water supply because a change in anultrapure water use condition required by a particular point of use,caused by a replacement of any production facilities in the plant, canbe accommodated by adapting or replacing only required functionalmodules. In addition, since the modular functional units can bemanufactured on a module basis in a module manufacturing plant, areduction in construction time and cost can be accomplished byinstalling the pure water system in a plant.

Preferably, the primary pure water system 12 and subsystem 14 in thepure water system 10, are implemented by devices which use at leastmembrane processing techniques. In particular, the primary pure watersystem 12 preferably comprises a reverse osmosis membrane device, adegas membrane device, and an electric deionization device.

The conventional primary pure water system 3 illustrated in FIG. 1generally produces the primary pure water mainly based on any of an ionexchange resin method, a combination of the ion exchange resin methodwith a reverse osmosis membrane, and a combination of the reverseosmosis membrane with an ion exchange resin method, with a vacuumdegasifier combined therewith.

However, the ion exchange resin method which dominates the processinghas the following problems when it is directed to a small-scaledsemiconductor plant or a small-scaled plant intended by the presentinvention, even though it is a low-cost, well-established technique forproducing a large amount of primary pure water over 100 m³/h for alarge-scaled semiconductor device manufacturing plant or a large-scaledplant.

Since the ion exchange resin method adsorbs impurities to an ionexchange resin for purification, a restore operation must be doneapproximately once a day for removing the impurities from the ionexchange resin. As such, the ion exchange resin method involves acomplicated operation management, and since no primary pure water can beproduced during the restore operation, primary pure water must bepreviously produced and stored in a tank such that pure water isavailable even during the restore operation.

In a small-scaled plant, the pure water supply system tends to occupy alarge percentage of the plant area. However, the pure water system mustbe provided with a primary pure water system 12 and a pure water tank 13having large capacities in order to reserve primary pure water for usein the restore operation, leading to a further increase in the arearequired for the pure water supply system. In addition, the recovery ofthe ion exchange resin involves the use of a large amount of chemicalswhich must be carefully handled, such as base, caustic soda and thelike, and the production of a large amount of strong acid and strongalkali chemical waste water which requires a complicated waste watertreatment.

Moreover, the vacuum degasifier must be approximately 10 meters high,irrespective of the processing capacity, and requires a dedicated cradlefor installation, so that careful attention should be paid to thebuilding construction.

On the other hand, the electric deionization device suitable for theprimary pure water system 12 in the pure water system according to oneembodiment of the present invention is free from the aforementionedproblems associated with the ion exchange resin method, and cancontinuously produce highly pure water, when combined with a reverseosmosis membrane, without the need for chemicals used in theregeneration. Also, when a degassing membrane is installed between thereverse osmosis membrane and electric deionization device, it candeoxidize as well as decarbonate without the problems associated withthe vacuum degasifier as mentioned above, to reduce an ion load on theelectric deionization device, permitting a continuous supply of highlypure water to be readily produced.

While any commercially available electric deionization device can beemployed for use as the primary pure water system 12, an electricdeionization device (manufactured by Ebara Corporation under the productname of GDI) disclosed in WO99/48820 or Japanese Patent PublicDisclosure No. 2001-121152 is preferably employed for simplification ofthe system configuration.

When GDI is employed, one reverse osmosis membrane is needed only infront of GDI because GDI is by nature not prone to precipitation ofhardness components. Thus, unlike other electric deionization devices,GDI does not need two reverse osmosis membranes for mostly removinghardness components or a combination of a reverse osmosis membrane witha water softener.

Further, since GDI excels in removal of total organic carbon (TOC),water processed by GDI can readily achieve TOC equal to or less than 15ppb which is an indicator of primary highly pure water. Other electricdeionization devices exhibit low TOC removal characteristics and maysuffer from elution of TOC from an ion exchanger filled in the electricdeionization devices. Therefore, for holding TOC at 15 ppb or lower withstability, a reverse osmosis membrane for removing TOC or an ultravioletirradiation device for decomposing TOC should be provided subsequent tothe electric deionization device to produce similar results, though theresulting system is rather complicated.

It should be understood that an arbitrary electric deionization deviceother than GDI is employed for the primary pure water system 12, andthat an arbitrary pure water systemsuch as the conventional systemillustrated in FIG. 1-4 is applicable to the pure water system 10 in thepresent invention.

Each of the point of use 30 operates independently of one another aslong as it uses each quality grade of pure water within its limits. Forexample, a large cleaning equipment, a small cleaning equipment, a CMPequipment and a lithography equipment require quality grades of purewater, respectively, as shown in FIG. 4. Even when supply pipes arerouted to provide a plurality of quality grades of pure water, thepiping system is not so complicated because the small-scaled plant hasonly a small number of points of use 30.

In operation, each of the points of use 30 communicates a “use requestsignal” to the controller 20 for using a particular quality grade ofpure water as shown in FIG. 4 in accordance with a preset pure water usepattern. The use request signal includes information declaring that aparticular point of use 30 desires to start using pure water, as well asan equipment ID indicative of a point of use 30 which transmits thesignal, a grade ID indicative of a particular grade of desired purewater, the amount of water, a use time (period), and the like, by way ofexample.

Alternatively, the information related to a use time may not be includedin the use request signal, and a “use end signal” may be sent from thepoint of use 30 to the controller 20. The use end signal may includeinformation indicative of the end of use of pure water or a notice ofthe end, and an equipment ID.

When the pure water use DB 21 (or another arbitrary storage device) ofthe controller 20 stores a pure water use pattern for each point of use30 along which the processing is advanced at each point of use 30, theuse request signal need not include the grade ID (or the grade ID,amount of pure water, use time (period)).

Based on the received signals, the controller 20 determines a timing atwhich an associated point of use 30 can use an appropriate grade of purewater circulated through supply pipes from the pure water system 10, andnotifies the point of use 30 of a “use permission signal” indicative ofpermission for use of pure water at the determined timing. Thecontroller 20 may be configured to control the operation of a recoveryprocessing (not shown) and the pure water system 10 themselves.

The following description will be centered on the ability to reduce theamount of instantaneously used pure water for providing a reduction inthe scale of the pure water system through the control conducted by thecontroller 20 with reference to a specific example.

The large cleaning equipments (WET1, WET2) 31, which are examples of thepoints of use, use ultrapure water for final rinse water, as shown inFIG. 4, however, these cleaning equipments 31 use the pure water inapproximately 40% of their overall operations, and use the final rinsewater, i.e., the ultrapure water in approximately 17% of their overalloperations. Therefore, as shown in FIGS. 5A and 5B, when the two largecleaning equipments simultaneously operate, they will need the ultrapurewater during the same time period with the possibility of approximately1% (when viewed from an overall operating time of the semiconductorplant). One of the large cleaning equipments requires the ultrapurewater for its operation for approximately 11% of the overall operatingtime. In the remaining 88% of the operating time, any of the two largecleaning equipments is not operating in a final rinse step, so that theultrapure water is not required at all. From the foregoing, when the twolarge cleaning equipments simultaneously request for the ultrapurewater, the second requesting cleaning equipments is kept waiting for thesupply of ultrapure water. In this way, the subsystem (ultrapure waterproducer) 14 of the pure water system 10 can be reduced in scale to 20liters per minute (L/m) which is essentially the amount supplied to onecleaning equipment.

A primary water supply system, i.e., the primary pure water system 12,pure water tank 13 and circulation system 15 can also be reduced inscale in a similar manner. Specifically, as shown in FIG. 4, the primarypure water is required by four cleaning equipments 31, five CMPequipments 32, and one lithography equipment 33, all of which constitutepoints of use. The percentage of an operating time requiring the primarypure water to an overall operating time, and the amount of requiredprimary pure water at each of the points of use 30 are, for example, asshown in FIGS. 6A and 6B. Based on the percentages of operating timesand the amounts of required primary pure water shown in FIG. 5, therequired primary pure water amounts to 50 L/m with possibility of 30%,and to 100 L/m at maximum with possibility of 76% (=30+46), and to 150L/m at maximum with possibility of 97% (=30+46+21).

Therefore, it is not necessary to provide a primary pure water systemwhich is capable of supplying the primary pure water at 176 L/m which isa simple sum of the amounts of primary pure water required by therespective points of use 30. Rather, the primary pure water supplysystem only needs to have the capability of supplying the primary purewater at 50 L/m, 100 L/m or 150 L/m depending on how many points of useare permitted to simultaneously use the primary pure water, therebyreducing the scale of the primary pure water supply system. For example,with the primary pure water supply system capable of supplying theprimary pure water at 100 L/m, when an additional point of use requestsfor the primary pure water while two point of use 30 are using theprimary pure water, the last requesting point of use may be kept waitingfor the primary pure water. Such simultaneous use requests can be madewith possibility of as low as approximately 21% in the example of FIGS.6A and 6B, and moreover, the primary pure water is requested only for ashort time period, so that the foregoing control strategy will hardlyaffect the processing in the overall plant.

As is apparent from the foregoing, according to the present invention,the pure water can be supplied without impediments to the manufacturingof semiconductor devices even with small capabilities of supplying theprimary pure water and ultrapure water, as long as the pure water issupplied to each point of use 30 from an appropriately controlled starttiming.

The pure water supply control operation performed by the controller 20in accordance with the present invention will be described in greaterdetail with reference to a flow chart of FIG. 7. This control isexecuted by a software program installed in a computer.

As a plurality of points of use 30 in the plant start operatingindependently of one another after the opening of the plant, thecontroller 20 waits for a use request signal and a use end signal atstep S1. In this event, the use request signal includes informationindicative of an equipment ID, a grade ID and the amount of requiredpure water, while the use end signal includes an equipment ID.

Upon receipt of the use request signal, the program proceeds to step S2where the controller 20 searches the pure water use DB 21 based on thegrade ID of pure water in the use request signal to determine whether ornot the requested grade of pure water is now being used by any point ofuse. When the requested grade of pure water has already been used, theprogram proceeds to step S3 where the controller 20 determines from thecapability of the pure water system 10 to supply the requested grade ofpure water whether or not the amount of pure water requested by the userequest signal can be immediately supplied to a requesting point of use.

At step S3, the controller 20 searches the pure water use DB 21 todetermine whether or not another point of use is waiting for therequested grade of pure water, and determines that the grade of purewater cannot be supplied in the requested amount if such a point of usealready exists. On the contrary, if no other point of use is waiting forthe requested grade of pure water, the controller 20 determines that thegrade of pure water can be supplied. In addition, when no other usepoint is waiting, the controller 20 determines from the capabilities ofthe pure water system 10 to supply pure water whether or not the purewater system 10 can supply the grade of pure water requested by thenewly requesting use point 30.

When the controller 20 determines at step S2 that the requested grade ofpure water is now in use and determines at step S3 that the requestedgrade of pure water cannot be supplied, the controller 20 sends a waitinstruction signal to the associated point of use 30 at step S4 forinstructing the point of use 30 to wait for the requested grade of purewater, and writes a waiting mark into the pure water supply DB 21 inassociation with the equipment ID and grade ID. In this event, thecontroller 20 also stores the requested amount of pure water in the purewater use DB 21.

On the contrary, when the controller 20 determines at step S2 that therequested grade of pure water is not in use, or when the controller 20determines at step S3 that the requested grade of pure water can besupplied, the controller 20 writes a supply start mark into the purewater use DB 21 in association with the equipment ID and grade ID in theuse request signal, and stores the requested amount of pure water. Inaddition, the controller 20 sends a use permission signal to the pointof use 30 corresponding to the equipment ID, thereby permitting thepoint of use 30 to use the requested grade of pure water.

On the other hand, when the controller 20 receives a use end signal atstep S1, the program proceeds to step S6 where the controller 20 writesa supply end mark in the pure water use DB 21, in association with theequipment and grade IDs. Then, at step S7, the controller 20 searchesthe pure water use DB 21 for an equipment ID which is given a waitingmark in association with the grade ID. The program proceeds to step S8when such a waiting mark is found, and returns to step S1 if not, wherethe controller 20 again waits for another signal. At step S8, thecontroller 20 reads from the pure water use DB 21 the amount of purewater which is stored in association with a grade ID that has been givena waiting mark at the earliest time point with respect to the grade ID.Then, the program proceeds to step S2, where the controller 20determines, as described above, whether or not another use point isusing the grade of pure water, followed by execution of steps S3 to S5.

In the foregoing manner, the controller 20 determines, from thecapabilities of the pure water system 10 to supply respective grades ofpure water, whether or not a requested grade of pure water can beimmediately supplied to a requesting use point 30 in a requested amount.The controller 20 does not permit the point of use 30 to use the purewater when not available, until the pure water system 10 can supply thepure water. In this way, even when the pure water system 10 isrelatively limited in the capabilities of supplying each grade of purewater, products can be manufactured without substantially degrading theproduction efficiency of the products.

The operation for controlling the supply of pure water described aboveis based on the premise that a plurality of points of use 30 cansimultaneously use the same grade of pure water within the capabilitiesof the pure water system 10 to supply pure water. Alternatively, thesupply of pure water may be controlled such that two or more points ofuse 30 are not at all permitted to use the same grade of pure water. Inthis event, when the controller 20 receives a use request signal from acertain point of use for a grade of pure water which has already beenused by another point of use, the controller 20 may not transmit a usepermission signal to the former point of use until a use end signal issent from the latter point of use.

Also, as previously described, when the use request signal includesinformation on a use timeperiod, the use end signal need not becommunicated from the point of use 30 to the controller 20, in whichcase the controller 20 waits only for the use request signal at step S1,resulting in elimination of the processing at steps S6 to S8 in FIG. 7.Further, when the controller 20 has previously known how long each pointof use 30 will use pure water, the controller 20 may automaticallydetermine that the point of use 30 has finished using the pure water ina predetermined time after the point of use 30 has started using thepure water. In this event, the point of use 30 does not need to send theuse end signal as well.

Preferably, points of use which do not simultaneously request for thesame grade of pure water are collected into a group. In this event, thegroup preferably includes at least two equipments having the samefunction, i.e., which continuously perform processing. This is because arandomly created group would experience difficulties in reconstructionthereof, as would be needed when some equipments are exchanged, andwould fail to sufficiently exert the effect of reducing the amount ofsupplied pure water without adversely affecting the productionefficiency.

While a preferred embodiment of the material supply system according tothe present invention has been described in connection with a pure watersupply system, it should be apparent to those skilled in the art that avariety of modifications can be made thereto. For example, in theexemplary pure water supply system, the controller 20 returns a waitinstruction signal to a point of use 30 which has sent a use requestsignal when the controller 20 does not immediately permit the use point30 to use requested pure water. However, the controller 20 does notnecessarily return the wait instruction signal. Also, the use permissionsignal may be used to open a pure water take-in valve associated withthe requesting point of use 30. Further, it should be understood thatthe present invention is not limited to pure water supply but may beapplicable to supply of an arbitrary gas, liquid or solid material.

Second Embodiment

FIG. 8 illustrates a material supply system for use with a silicon filmLPCVD equipment (Low Pressure Chemical Vapor Deposition) for performingan LPCVD process using a monosilane gas in accordance with a secondembodiment of the present invention.

The LPCVD equipment (semiconductor manufacturing) 40, which is one ofprocessing facilities in a semiconductor device manufacturing plant, isinstalled on a Fab floor within a clean room which also contains areaction tube 41 or chamber made of highly pure quartz. The reactionpipe 41 is supplied with a monosilane gas which is a material gas foruse in the LPCVD deposition, and a fluorine gas for etching siliconfilms deposited on the inner wall of the reaction tube 41, othercontained quartz, and surfaces of parts made of silicon carbide to cleanthe interior of the reaction tube 41. These gases are introduced from amonosilane gas cylinder 51 installed outside the clean room and afluorine gas generator 52 installed on the floor below (SUB-Fab floor)within the clean room, respectively, through a buffer (gas buffer) 42.Pipes for introducing the monosilane gas and fluorine gas to the buffer42 are closed by air operation valves 46.1, 46.2, respectively, and apipe connecting the buffer 42 to the reaction tube 41 is closed by asimilar air operation valve 45.

An operation for supplying the fluorine gas for cleaning will bedescribed later in a third embodiment.

A pressure gage 43 measures a pressure at which the buffer 42 is filledwith a gas. For purging the interior of the buffer 42 and reaction tube41, a dilute gas produced during a reaction is supplied, or a nitrogengas is supplied from a nitrogen gas generator 53 through a valve 46.3for restoring the pressure within the reaction tube 41 to theatmospheric pressure. A gas supplied from the buffer 42 to the reactiontube 41 is heated therein, and exhausted therefrom by a vacuum pump 54installed on the floor below in the clean room through a gate valve 48which has both a function of adjusting the pressure within the reactiontube 41 and a shut-down function, after an LPCVD reaction or an etchingreaction, together with gases produced by the reaction and the unreactedgas, by adjusting the conductance of the fluid with the opening of thevalve 46.3. The exhausted gas is discharged from an exhaust duct 56provided in the clean room after it is rendered harmless by an gasabatement equipment 55.

A semiconductor wafer under processing is placed within the reactiontube 41 in which the LPCVD reaction takes place, and the reaction tube41 is heated by a heater 47 in this state. The valves 45, 46.1-46.3, 8,heater 47, fluorine gas generator 52, vacuum pump 54, and gas abatementequipment 56 are controlled by an equipment controller 49 for performingand managing the LPCVD process. The outputs of the pressure gage 43 andheater 47, the temperature within the reaction tube 41, the pressurewithin the reaction tube 41, and the like are also applied to thecontroller 49. Information on deposition is output from a productmanagement database (DB) 71 to the equipment controller 49 through a LAN60.

Deposition of a polycrystalline silicon film is performed using theLPCVD equipment 40 illustrated in FIG. 8 as described below. Before anunprocessed semiconductor wafer reaches the process in the LPCVDequipment 40, detailed information on the LPCVD process performed by theLPCVD equipment 40 is applied to the equipment controller 49 from theproduct management database 71. For example, assuming that the LPCVDprocess deposits a polycrystalline silicon film of 100 nm thick at 620°C. and 0.2 Torr for ten minutes using a monosilane gas at a flow rate of100 sccm, the total amount of monosilane gas used for the deposition iscalculated by:100 SCCM×10 minutes=1000 SCC

It is assumed that the buffer 42 associated with the LPCVD equipment 40has an inner volume of 1000 cc. Under the control of the controller 49,after the valve 45 is once opened, the buffer 42 is evacuated to asufficiently low pressure by the vacuum pump 54. Then, the valve 45 isclosed and the valve 46.2 is next opened to introduce the monosilane gasinto the buffer 42. After the buffer 42 is filled with 1000 SCC of themonosilane gas (a volume of 1000 cm³ under a standard gas state), thevalve 46.2 is closed to shut off the buffer 42.

The monosilane gas filled in the buffer 42 can be controlled by avariety of methods. FIGS. 9A-9C show three exemplary alternatives.

FIG. 9A shows a method of adjusting the pressure within the buffer 42.Specifically, this method entails a pressure reducing valve disposedupstream or downstream of the valve 46.2 for automatic adjustment to adesired pressure in response to an instruction from the equipmentcontroller 49. In this event, the pressure reducing valve adjusts thepressure within the buffer 42 at atmospheric pressure, and 1000 SCC ofmonosilane gas is measured.

FIG. 9B shows a method of measuring 1000 SCC of monosilane gas by theflow rate and time using a mass flow controller (MFC) disposed upstreamor downstream of the valve 46.2. For example, the monosilane gas isconstantly supplied at a flow rate of 2 SLM for 30 seconds. Here, a moreeconomical mass flow meter may be used instead of the mass flowcontroller to measure 1000 SCC of monosilane gas from an accumulationvalue output therefrom.

FIG. 9C shows a method of controlling the pressure within the buffer 42by measuring the pressure within the buffer 42 using the output of thepressure gage 43 mounted to the buffer 42, and closing the valve 42.6when the pressure reaches a desired value, 1 hPa (=760 Torr) in thisevent. When the pressure rapidly increases, an orifice or the like maybe provided for reducing the conductance of the fluid, or a piezo valvemay be provided for adjusting the conductance through its opening, tocontrol the pressure within the buffer 42 to 760 Torr with the openingfed back from the value of the pressure gage 43.

In the methods described above, the pressure adjuster, mass flowcontroller, and/or conductance controller may be disposed upstream of alocation at which the monosilane gas is branched to other s, such thatthese devices, which are relatively expensive parts, can be shared by aplurality of semiconductor manufacturing equipments such as the LPCVDequipment and the like. When the flow rate is not measured using themass flow controller or mass flow meter as in the methods shown in FIGS.9A and 9C, the gas must be at a standard temperature and a standardpressure for precisely controlling the total flow rate. In this event,therefore, a pressure set value must be corrected by adjusting ormeasuring the state or the temperature of the buffer 42. It is criticalto select an optimal combination from the balance between a particularapplication and required specifications and cost of a product.

In any of the methods described above, the monosilane gas can besupplied in a shorter time period irrespective of an actual time takenfor the deposition, so that the monosilane gas cylinder cabinet 51 maybe actually connected to the LPCVD equipment 40 for a shorter timeperiod. In addition, the monosilane gas may be supplied before thedeposition is actually started to significantly reduce the influence ofa failure or a reduction in the supply due to accidents, faults, andartificial mistakes in the plant on the actual LPCVD manufacturingprocess, thereby providing for stable manufacturing. On the other hand,the monosilane gas may be supplied slowly for a longer time than thetime required for deposition using more economical apparatuses thanconventional supply facilities in terms of the space and cost.

After the buffer 42 is filled with the monosilane gas, or in parallelwith this operation, an unprocessed substrate is introduced into thereaction tube 41. After the reaction tube 41 is evacuated, thetemperature and pressure are adjusted to desired values, here 620° C.and 0.2 Torr, respectively. Also, other preparatory operations should beprogressed prior to the deposition.

For the deposition, a mass flow controller may be disposed downstream ofthe valve 45 to control the flow rate (see FIG. 10A). Alternatively, thevalve 45 may be provided with an additional function of adjusting theconductance with its opening, or a valve capable of adjusting theconductance, such as a piezo valve may be used in combination to adjustthe opening to constantly reduce the output value of the pressure gage43 mounted to the buffer 42 (in this event, substantially at a rate of76 Torr/min because the monosilane gas at 760 Torr is used up in tenminutes), thereby making it possible to control the flow rate withoutusing the mass flow controller (see FIG. 10B). By thus controlling theflow rate during the deposition, 1000 SCC of monosilane gas for use inthe deposition need not be precisely measured beforehand. After thedeposition with 100 SCCM of monosilane gas for ten minutes, theremaining monosilane gas can be wasted through a bypass line by thevacuum pump 54, without being passed through the reaction tube 41, ormay be saved for the next deposition.

An example is next given, where the present invention is applied to abatch type LPCVD equipment for depositing polycrystalline silicon filmson a plurality (generally 100 to 200) of semiconductor wafers disposedin the reaction tube 41 at one time. In a batch type vertical LPCVDfurnace, semiconductor wafers are vertically stacked at predeterminedintervals (for example, approximately 5 mm) in the reaction tube 41.After the reaction tube 41 is stabilized at a reaction temperature(here, 620° C.), a monosilane gas or material gas is supplied at acontrolled flow rate by a mass flow meter or the like. It should benoted that the gas introduced into the reaction tube 41 is consumed inan upstream region to produce reaction product gases, so that theintroduced gas has a relatively low concentration in a downstream regionto slow down the deposition reaction.

In the embodiment herein illustrated, the monosilane gas is consumed inthe deposition reaction and vapor phase reaction to cause the followingchemical reactions:SiH₄ ? SiH₂+H₂ (vapor phase)SiH₄ ? Si+2H₂ (on surface of deposited film)SiH₂ ? Si+H₂ (on surface of deposited film)

Produced SiH₂ (silylene gas) and H₂ (hydrogen gas) cause a reduction inthe partial pressure of SiH₄ (monosilane gas) in the downstream to slowdown the deposition rate. Therefore, when the monosilane gas iscontinuously supplied at a certain flow rate (here, 100 SCCM) into thereaction tube 41 which contains a plurality of semiconductor wafersstacked one above the other, the deposition rate is reduced on thosepositioned on the downstream side for the reason set forth above. Themonosilane gas is carried from the peripheries to the centers of thesemiconductor wafers by diffusion through narrow spaces between thestacked semiconductor wafers (in this embodiment, narrow spaces ofapproximately 5 mm), as compared with the radius of the semiconductorwafers. Thus, in this example, the peripheral region corresponds to theupstream side, while the central region corresponds to the downstreamside. As a result, the deposition is performed in the peripheral regionat a rate higher than in the central region, resulting in a smallerthickness of the deposited film in the central region, which dominates alimitation to the uniformity of deposition, as is well known in the art.

When the flow rate of the monosilane gas from the buffer 42 iscontrolled during the deposition by a method using a mass flowcontroller as shown in FIG. 10A or by a method as shown in FIG. 10B, thedeposited film is similar in uniformity. However, with the use of thebuffer 42, it is possible to control the amount of monosilane gassupplied for use in the deposition by a total amount of introduced gas,without managing the flow rate at all, as shown in FIG. 10C. Thiscontrol sequence associated with the deposition will be described below.

First, a required amount of monosilane gas is measured and filled in thebuffer 42. Then, the reaction tube 41 is sufficiently evacuated by thevacuum pump 54 to 0.1 mTorr, for example, and the gate valve 48connected to the vacuum pump 54 is completely shut off to enclose thebuffer 42. Subsequently, the valve 45 connecting the buffer 42 to thereaction tube 41 is fully opened to fill the reaction tube 41 with theamount of monosilane gas required for the intended deposition in severalseconds at a stretch. Even in the narrow spaces between respectivewafers, the monosilane gas is filled at a stretch. By thus diffusing themonosilane gas at a rate sufficiently higher than the reaction rate, thedeposition can provide a high uniformity in film thickness withoutcausing a non-uniform film thickness due to the diffusion controlledrate of the gas as mentioned above.

FIG. 10D shows a change over time in the concentration of the monosilanegas, and FIG. 10E shows a change in the deposition rate and a changeover time in the thickness of a deposited film. Unlike a generaldeposition performed with a monosilane gas introduced at a controlledflow rate by a mass flow controller or the like, the deposition rate isnot constant. A target film thickness must be found by integrating dataon the deposition rate, and determining a deposition time based on thegraph shown in FIG. 10E. Since the deposition rate is initially high,gradually decreases, and is very slow near the target film thickness,the film thickness can be controlled more precisely in a short timeperiod with a reduced error in film thickness due to the time variation.

Instead of an undoped silicon film, when a deposited film is doped withimpurities which serve as doners or acceptors such as arsenic, boron,phosphorous or the like, or germanium belonging to the same group VIduring the deposition, an additional buffer equivalent to the buffer 42may be previously provided for storing a source gas such as ASH₃(arsine), BeH₆ (diborane), PH₃ (phosphine), GeH₄ (germane) or the likefor use in the deposition process in a procedure similar to the processwhich uses monosilane. Further, these gases may be mixed with amonosilane gas and stored in the same buffer 42 to provide a uniformconcentration of dopant. In this event, a mass spectrometer or aninfrared absorption spectrometer may be connected to the buffer 42 tooutput the result of analysis to the equipment controller 49 whichcontrols a lead valve or the flow to the buffer 42 to correctly know theconcentration of each of the components before they are used for thedeposition to control the concentration of each gas which is to befilled in the buffer 42. Alternatively, the pressure gage 43 may simplymeasure an increment in the pressure in the buffer 42 as the respectivegases are filled in the buffer 42 one by one to calculate a mixtureratio of each gas. Variations in the subsequent deposition are similarto the deposition using a monosilane gas alone.

When the present invention is applied to LPCVD deposition of tantalumoxide using penthaethoxytantalum (hereinafter abbreviated as PET)instead of the deposition of a silicon film using a monosilane gas, arequired amount of PET which is a liquid at an atmospheric pressure anda room temperature is measured by a flow control based on a liquid massflow, weight, level, or the like, and injected into the buffer 42. Thebuffer 42 may be provided with a heater 47 and a temperature adjuster(not shown) for adjusting the temperature to maintain a state in whichPET evaporates but does not thermally react to change PET from a liquidto a gas which can be stored. This process is illustrated in FIG. 11A.The subsequent deposition is similar to that using a monosilane gas. Inthis way, the amount of gas required for the deposition can be suppliedwithout giving rise to problems such as an insufficient amount of gassupplied due to limited capabilities of an evaporator or the like to theLPCVD reaction in the vapor phase by a source which is a liquid or asolid at a room temperature. Likewise, ruthenium ethylcyclopentane foruse in LPCVD deposition of ruthenium is a liquid source and can betreated in a similar manner to PET. However, since rutheniumcyclopenthane which is a material for ruthenium CVD is a solid, it isheated for evaporation after it is supplied to the buffer 42 in agranular or pellet form. This process is illustrated in FIG. 11B. Inthis event, the amount of a solid source is managed by weight or thenumber of pellets. LPCVD performed after the source is evaporated andstored is performed in a similar manner to the counterpart using amonosilane gas.

Third Embodiment

A third embodiment will next be described in connection with an examplein which a silicon film on the inner wall of the reaction tube 41 iscleaned or washed-off using a fluorine gas after a polycrystallinesilicon film has been deposited using the silicon film LPCVD equipment40 illustrated in FIG. 8 as described above.

Before the cleaning, details on cleaning and etching to be nextprocessed by the apparatus, such as etching conditions and the likebased on a current film thickness on the quartz tube, are input to theequipment controller 49 from an equipment management database 72 (FIG.8). For example, this is peel-off of 100 nm of a polycrystalline film,which entails LPCVD deposition that is performed at 10 Torr and 300° C.for five minutes with a fluorine gas at a flow rate of 1000 sccm. Thetotal amount of fluorine gas used in the deposition is calculated asfollows:1000 SCCM×5 minutes=5000 SCC

It is assumed that the buffer 42 has an inner volume of 5000 CC. Underthe control of the equipment controller 49, as the valve 45 is opened,the buffer 42 is evacuated to a sufficiently low pressure by the vacuumpump 54. Then, the valve 45 is closed and the valve 46.1 is next openedto introduce the fluorine gas into the buffer 42. After the buffer 42 isfilled with 5000 SCC of the monosilane gas (a volume of 5000 cm³ under astandard gas state), the valve 46.1 is closed to shut off the buffer 42.Assuming that the fluorine gas is produced by the fluorine gas generator52 through an electric decomposition reaction of KF.2HF, or a thermaldecomposition chemical reaction of KF.6HF, when the fluorine isgenerated at approximately 100 SCCM/minute, a fluorine gas generatorhaving a scale ten times as large as the current one would be requiredto provide the fluorine gas at a flow rate of 1000 SCCM which isrequired by the etching conditions, when the fluorine gas is directlysupplied to the LPCVD furnace without using the buffer 42. However, thefluorine gas generator fully operates only for five minutes in which theetching reaction is performed, and is not needed in the rest of theprocess.

The present invention can support a process which requires a fluorinegas at a flow rate of 1000 SCCM using the fluorine gas generator 52which is capable of supplying merely 100 SCCM by starting storing thefluorine gas in the buffer 42, 50 minutes before the etching is started.The storage of the fluorine gas in the buffer 42 can be startedimmediately after a monosilane gas has been removed from the buffer 42following the end of the previous deposition, so that the fluorine gascan be filled in the buffer 42 in a time period allocated to purge thereaction tube 41, a time period allocated to restore a normal pressure,a time period allocated to remove a semiconductor wafer, and a timeperiod allocated to evacuation and thermal stability for etching. Also,an additional dedicated buffer may be provided other than a buffer for amonosilane gas to fill the buffer with the fluorine gas immediatelyafter the previous etching. Generally, the cleaning and etching isperformed at a lower frequency than the deposition, so that theinvestment, space and the like can be reduced by further reducing thecapabilities to supply the fluorine gas.

The processing in the LPCVD equipment 40 in the cleaning process issimilar to the deposition process using a monosilane gas. Particularly,in the cleaning process, the end of etching can be often monitored inreal time by the end of a rise in temperature in the reaction tube 41 orby an analysis on exhaust gases. This is quite useful because a changeover time in the etching rate need not be measured beforehand forcontrolling the total amount of introduced gas without using the flowrate control illustrated in FIG. 10C.

When the reaction tube 41 is isolated for reaction as illustrated inFIG. 10C, an additional buffer may be provided on the exhaust side, asillustrated in FIG. 12A, to return a recovered etching gas again to thebuffer 42 for use in the next etching. This can increase a utilityefficiency of the material gas, reduce the cost and save energy.

As illustrated in FIG. 12B, not only for materials used in theprocessing and reaction in the processing facilities, an additionalbuffer may be provided, for example, before the exhaust gas abatementequipment 55 to adjust the flow rate of exhaust gases which exceed theprocessing ability of the gas abatement equipment 55. Though the gasabatement equipment 55 effectively operates only when harmful gases areexhausted, a buffer may be provided before the gas abatement equipment55, permitting a common use of the gas abatement equipment 55 tocollectively process exhaust gases from a plurality of processingfacilities. Even if exhaust gases simultaneously emitted from aplurality of facilities or a large amount of exhaust gases emitted froma single process exceed the processing rate of the gas abatementequipment 55, the exhaust gases can be temporarily stored in the buffersuch that the exhaust gases are sent into the gas abatement equipment 55from the buffer at a rate below the processing rate of the gas abatementequipment 55, thereby removing surplus gas abatement equipment 55.

Fourth Embodiment

Referring next to FIG. 13, a fourth embodiment will be described inconnection with a system which employs a plurality of silicon film LPCVDequipments 40 illustrated in FIG. 8 to clean the reaction tubes 41 inthe plurality of LPCVD equipments.

Similar to the LPCVD equipment 40, LPCVD equipments 40.1, 40.2 are eachsupplied with a fluorine gas from the fluorine gas generator 52, andcontrolled by a CIM server 73 in the plant through an in-plant LAN 60and equipment controllers 49.1, 49.2. A distribution controller 52-4 forcontrolling branch valves 52-0-52-25 to the fluorine gas generator 52and respective LPCVD equipments 40, 40.1, 40.3 are also controlled bythe CIM server 73.

The CIM server 73 classifies and stores process orders and types ofrespective lots of unprocessed semiconductor wafers, and priorities ofmanufacturing for other lots in manufacturing lines as emergencydegrees. In this way, the CIM server 73 manages a manufacturing scheduleas to when and which lot is processed. The CIM server 73 also calculatesa currently accumulated film thickness in the reaction tube in eachLPCVD equipment, automatically calculates a film thickness for whichcleaning is recommended from data including transitions in a sequence ofthe film thickness of the deposition and dust, and a sequence of thefilm thickness and deposition dust after previous cleaning, and thelike. The recommended film thickness may be set by a human. The CIMserver 73 has a function of scheduling when the reaction tubes arecleaned from current waiting lots and future manufacturing schedule.

In this system, equipments which should be first cleaned (i.e., whichuse a fluorine gas) are given higher priorities in the scheduling. Forexample, when the LPCVD equipment 40 should first be cleaned, the valve45 is opened from the CIM server 73 through the equipment controller 49,and the controllers 49.1, 49.2 of the other LPCVD equipments 40.1, 40.2close the valves 45.1, 45.2, respectively.

Next, as the CIM server 73 is notified from the equipment controller 49that a required amount of fluorine gas, calculated from an accumulatedfilm thickness, has been stored in the buffer 42, controlled by any ofthe methods as illustrated in FIGS. 9A to 9C, the CIM server 73 controlsthe start of storing the fluorine gas in the buffer 42 in a similarmanner in either the LPCVD equipment 40.1 or 40.2 in accordance with thenext priority set therein.

When no buffer in any LPCVD equipment 40, 40.1, 40.2 is used after allthe storages are completed, the fluorine gas is stored in a buffer 52-3contained in the fluorine gas generator 52 up to its pressure limit.When there is a further time available, the CIM server 73 stops theoperation of the fluorine gas generator 52. Through these operations,the fluorine gas generator 52 can be used in an effective way, resultingin optimization or minimization of resources such as the cost, space,maintenance and the like of the scale.

By controlling the buffer 52-3 in the fluorine gas generator 52 and thebranch valves 52-0-52-2 by the distribution controller 52-4, the presentsystem can support any LPCVD equipment irrespective of whether itcontains a buffer. In this event, instructions from the CIM server 73are executed by the distribution controller 52-4 instead of theequipment controller 49 (and/or 49.1, 49.2). Assuming for example thatthe LPCVD equipment 40 is not provided with the buffer 42 while afluorine gas is being used, the valve 52-0 is opened in association withthe valve 45. In this way, the buffering function can be shared by aplurality of apparatuses.

Fifth Embodiment

Referring next to FIG. 14, a fifth embodiment of the present inventionwill be described in connection with processing facilities which includea plurality of semiconductor wafer cleaning equipments (three in FIG.14) and a refiner for condensing and recycling a hydrogen fluoridesolution.

In each of the cleaning equipments, a pipe branched from a hydrogenfluoride (HF) supply pipe 62 from the plant, and a return pipe 63 froman HF condensation/refinery equipment 57 are connected to respectivebuffers 42, 42.1, 42.2 of the cleaning equipments. The pipes connectedto the buffers are shut off by respective control valves, and each ofthe buffers is provided with a sensor (not shown) for measuring theamount of the solution stored in the buffer by level. Equipmentcontrollers 49, 49.1, 49.2 for controlling these buffers, associatedsensors, and control valves (import valves) (dedicated controllers maybe provided for these components) are associated with the respectivecleaning equipments, and controlled by a management DB server formanaging the cleaning equipments and LOT through a plant LAN 60. In eachof the cleaning equipments, the hydrogen fluoride (HF) solution used inthe processing of semiconductor wafers is partially consumed inreactions such as etching of silicon oxide films, and partially notconsumed, diluted by pure water or the like, drained, and oncetransported to the HF condensation/refinery equipment 57 through adischarge pipe 64.

The HF condensation/refinery equipment 57 filters and refines only ahydrogen fluoride component which is returned to the buffers 42, 42.1,42.2. Distribution to the respective buffers is instructed to buffercontrollers (not shown) via the LAN 60 through a calculation ofpriorities made by the CIM server 73, as is the case with the fourthembodiment, so that the hydrogen fluoride is preferentially distributedto those facilities which next need the hydrogen fluoride in accordancewith the instruction. When a semiconductor wafer under processing asksfor particularly normal hydrogen fluoride, such hydrogen fluoride issupplied to an associated buffer from a primary hydrogen fluoride sourcein the plant, and the hydrogen fluoride from the HFcondensation/refinery equipment 57 is supplied to the equipment which isgiven the second highest priority. When the equipment 57 cannot recoverhydrogen fluoride at a rate high enough to supply the hydrogen fluorideto requesting equipments at next time, hydrogen fluoride can becompensated from the primary hydrogen fluoride supply source in theplant in a similar manner.

Introduction of a lot can be delayed after the preceding lot has beencleaned by a cleaning equipment in order to fill the hydrogen fluoridebuffers with recovered HF in consideration of a cleaning time period inthe next manufacturing equipment stored in the lot management DB (notshown). In this way, according to the present system, the CIM server 73can manage the HF condensation/refinery equipment 57, buffers, andcleaning equipments to provide inexpensive hydrogen fluoride recoveredthrough reuse, using condensation/refinery equipment in a minimum scalewithout reducing a substantial manufacturing rate.

As described above, the material supply system according to the presentinvention can eliminate excessive supply capabilities and employ aminimally required scale of material supply facilities, as compared witha prior art example. It is therefore possible to reduce an initial costand a running cost of the material supply system to reduce a productioncost of products produced by a semiconductor device manufacturing plant.

Also, in the material supply system according to the present invention,since a material is temporarily stored in a buffer associated with eachprocessing facility before it is supplied to the processing facility, arequired amount of material can be supplied to each processing facilityeven if a primary material supply source has relatively low supplycapabilities.

It is further understood by those skilled in the field that the forgoingdescription is preferred embodiments of the invention and variouschanges and modifications may be made in the invention without departingfrom the spirit and scope thereof.

1. A material supply system for supplying the same kind of a gas, liquidor solid material to a plurality of processing facilities in asemiconductor device manufacturing plant, the system comprising: amaterial supply source; and a controller for controlling the supply ofthe material from a supply source to the processing facilities, suchthat a total amount of the material currently used by the plurality ofprocessing facilities does not exceed an amount of the material whichcan be supplied from the supply source, by controlling a start timingfrom which the material is supplied to a processing facility.
 2. Amaterial supply system according to claim 1, wherein: at least-two ofthe plurality of processing facilities are adapted to send to thecontroller use request signals for requesting to start using thematerial, or the use request signal and use end signals for notifyingthe end or an end notice of use of the material; and the controller isadapted to determine, upon receipt of the use request signal associatedwith the material currently used in at least one processing facilityfrom another processing facility, whether or not a total amount of thematerial required by these processing facilities exceeds the amount ofthe material which can be supplied by the supply source, and send a usepermission signal to the other processing facility to permit the otherprocessing facility to use the material when determining that the totalamount does not exceed.
 3. A material supply system for supplying thesame kind of a gas, liquid or solid material to a plurality ofprocessing facilities in a semiconductor device manufacturing plant, thesystem comprising: a material supply source; and a controller forcontrolling the supply of the material from a supply source to aplurality of processing facilities, such that the material is not usedsimultaneously by a plurality of processing facilities by controlling astart timing from which the material is supplied to a processingfacility.
 4. A material supply system according to claim 3, wherein: atleast two of the plurality of processing facilities are adapted to sendto the controller use request signals for requesting to start using thematerial, and use end signals for notifying the end or an end notice ofuse of the material; and the controller is adapted to respond to the userequest signal associated with the material currently used in at leastone processing facility from another processing facility by delayingsending a use permission signal for permitting the other processingfacility which has sent the use request signal to use the material,until the controller receives the use end signal from the processingfacility which is using the material.
 5. A material supply systemaccording to any of claims 1 to 4, wherein: the material supply sourceis a pure water system for producing a plurality of quality grades ofpure water; and the controller is adapted to control the supply of purewater to the processing facilities on a grade-by-grade basis.
 6. Amaterial supply system for supplying a gas, liquid or solid material toprocessing facilities in a semiconductor device manufacturing plant, thesystem comprising: a material supply source; a buffer for temporarilystoring the material; and a controller for controlling the supply of thematerial from the buffer to the processing facilities.
 7. A materialsupply system according to claim 6, further comprising control means forcontrolling the state of the material in the buffer, and/or measuringmeans for measuring the state of the material in the buffer.
 8. Amaterial supply system according to claim 6 or 7, further comprisingmeans for quantifying the amount of the material required at least insingle batch processing by one of the processing facilities.
 9. Amaterial supply system according to any one of claims 6 to 8, whereinthe buffer is adapted to simultaneously store at least two kinds or moreof materials, the system is adapted to supply the materials in the samebuffer to the same processing facilities.
 10. A material supply systemaccording to any one of claims 6 to 9, wherein materials react in thebuffer to produce a new material, and the new material are supplied tothe processing facilities from the buffer.
 11. A material supply systemaccording to any one of claims 6 to 10, further comprising control meansfor controlling the temperature, the pressure, and/or the concentrationof a material component in the buffer.
 12. A material supply systemaccording to any one of claims 6 to 11, wherein an etching gas is storedin the buffer, and further comprises means for supplying the etching gasto wash chambers in the processing facilities.
 13. A material supplysystem according to any one of claims 6 to 11, wherein pure water isstored in the buffer, and further comprises means for supplying the purewater to chambers in the processing facilities.
 14. A material supplysystem according to any one of claims 6 to 13, further comprising meansfor recovering the material discharged from a chamber at least one ofthe processing facilities to store the recovered material in the buffer.15. A material supply system according to any one of claims 1 to 14,wherein the system is adapted to supply the material from a singlesupply source to a plurality of processing facilities.
 16. A materialsupply system according to claim 15, wherein the supply source includesa buffer for temporarily storing the material.
 17. A semiconductordevice manufacturing plant having a plurality of processing facilities,comprising: a material supply system according to any one of claims 1 to16; database for logging and managing processes in each of theprocessing facilities; and a CIM-based control system for totallycontrolling the semiconductor device manufacturing plant, wherein thecontrol system sets a supply rate at which the material supply systemsupplies the material to the processing facilities, and priorities forsupplying the material among the processing facilities based on anoperation schedule for the processing facilities, and a semiconductordevice manufacturing schedule on the database.